// 模块引用

// 引入系统模块(即由Node.js环境直接提供的模块)
const fs = require( 'fs' );

// 引用自定义模块
const arith = require( './arith.js' );
console.log( arith );

console.log( arith.add( 100 , 50 ) );
console.log( arith.sub( 100 , 50 ) );
console.log( arith.div( 100 , 50 ) );
console.log( arith.mul( 100 , 50 ) );

const math = require( './arith.js' );
console.log( math );

console.log( math === arith );